Former Secretary to the Government of the Federation, Mr Babachir Lawal, is in the custody of the Economic and Financial Crimes Commission (EFCC).
The EFCC Acting Head of Media and Publicity, Mr Samin Amaddin, confirmed this to Channels Television on Wednesday.
Mr Amaddin said the former SGF is cooperating with investigators and has been making useful statements.
He added that his interview with the anti-corruption agency would continue on Thursday.
Mr Lawal’s appearance at the EFCC custody comes about three months after he was sacked by President Muhammadu Buhari for allegedly violating the due process in the award of contracts under the Presidential Initiative on the North East (PINE).
Although the former SGF was earlier suspended on April 20, 2017, the President had appointed Mr Boss Mustapha on October 30, 2017, to replace Lawal.
The Presidency had, however, been hit with heavy criticism that the former SGF must be investigated after being sacked.
On its part, the EFCC had informed Channels Television three days after Lawal was sacked that it had set up a crack team to probe the fraud allegations levelled against him.
A source in the anti-graft agency had said the team, made up of special investigators from the EFCC, would examine all the details relating to the N200m contract for the cutting of grass in the North East linked to the former SGF.